The Ideal Transport Fuel
Hydrogen has been proposed as a transport fuel but it has many
problems in its pure form.
hydrogen gas molecule is very small and will pass through solid steel when
under pressure. This
means that in a compressed gas storage tank you can expect to lose about 1%
causes steels to become brittle. This
can ultimately lead to brittle fracture of pressurized steel containment
has a wide flammability range which makes it more of an explosion hazard
than any other fuel. Hydrogen has a flammability range from 4% to 75% as
compared to, methane at 2% to 9%.
has a low energy per unit volume compared with liquid fuels such as
methanol, and ethanol. Hydrogen
has a higher heating value of 11.7kJ/L and methane is 36.5kJ/L at 1bar
pressure and 25°C. Methanol’s
higher heating value of 18MJ/L is a 1000 times higher than that of hydrogen
at ambient conditions.
takes a great deal of energy to compress or liquefy it for transport and
storage. It takes approximately
18MJ/kg to compress hydrogen to 400bar, but only 2MJ/kg to compress methane
to the same pressure. To
liquefy hydrogen requires dropping the temperature to -253°C (20K), a
process of only 7% efficiency.
hydrides for storage have a high energy requirement to bind the hydrogen
into the metals, and then heat to release it again.
The hydrogen needs to be compressed.
The storage is inefficient with only 55-60kg(H2)/m³
compared with 71kg(H2)/m³ for liquid hydrogen and 100kg of hydrogen
contained in one cubic meter of methanol.
through pipe systems or by truck is very energy intensive.
To transport hydrogen gas at 200bar 200km by diesel truck will
consume 38% of the energy delivered, whereas methane at 200bar will consume
only 10% of the energy delivered. Liquid
fuels require only a fraction of a percent to deliver.
Piping hydrogen 1000km will consume 9% of the input energy value.
generation of hydrogen from other sources is inefficient.
Electrolysis is at best 70% efficient.
Reformation from coal and hydrocarbons is very energy intensive and
at best only 60% efficient.
generate electricity from hydrogen through a fuel cell is of the order of
The bond that hydrogen forms is still a good energy
source. So why not join the hydrogen up to carbon atoms on a carbon
chain? Is that not what hydrocarbons in gasoline are?
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